Radio spectrum is a vanishing resource and, for that reason, engineers in the United States Army and Navy are joining forces as part of an effort to develop a next-generation cognitive radio that could benefit commercial and military users alike. The Army's Communications- Electronics Research, Development, and Engineering Center (CERDEC), specifically the organization's Software Defined Radio (SDR) laboratory, will work with the Naval Research Lab (NRL), as well as with academic researchers, industry, and other Department of Defense (DoD) organizations with the goal of building a universal radio test bed for evaluating different cognitive radio designs.

A cognitive radio is essentially a self-configuring SDR. It must be able to detect different parameters about its operating environment and make decisions on its own configuration accordingly. For example, it must be able to detect available bandwidth and spectrum activity in order to switch to available bands, but also within regulatory requirements for a particular area. Because such requirements are geographic in nature, a cognitive radio must also have an awareness of the geography. It must make decisions on occupied bandwidth, available free channels, type of information to be transmitted (voice, video, or data) and how much power to use, and modulation types to be used for most efficient operation with available bandwidth. It must also take into account environmental conditions, such as multipath, fading, and possibly jammers and interference.

Based on previous in-house SDR initiatives, CERDEC will work with NRL to transition cognitive radio development to the GNU Radio's opensource, free software environment. GNU Radio is a volunteer organization that has created a free software development toolkit containing the signal-processing blocks for creating SDR designs with low-cost computers and external radio frequency (RF) hardware. Involvement with GNU Radio is done in an opensource environment where researchers can share their development efforts with other SDR developers. Until now, it has largely been fueled by work performed at leading academic institutions for the enhancement of commercial wireless communications, although some projects have also aimed at creating nextgeneration SDR-based tactical radios.

The GNU Radio site lists some of the published papers using the software from an impressive list of universities that includes Notre Dame, Virginia Tech's Center for Wireless Telecommunications (CWT), the University of Delaware, the University of California at Los Angeles (UCLA), the University of Maryland, Massachusetts Institute of Technology (MIT), University College London, and the University of Washington. GNU Radio applications are primarily written using the Python programming language, while the supplied, performance-critical signalprocessing path is implemented in C++ programming language using processor floating point extensions where available. Thus, the developer is able to implement real-time, high-throughput radio systems in a simple-to-use, rapid-applicationdevelopment environment. The GNU Radio toolkit includes a wide array of C++ signal-processing blocks, including signal sources, filters, modulators, demodulators, voice encoders and decoders, synchronization, equalization, Fourier transforms, wavelet transforms, and other mathematical functions.

GNU Radio was selected as the radio platform for the test bed due to its low cost, software flexibility, and accessibility. Additionally, the defense research organizations hope the GNU's open-source platform will lend itself to collaborative efforts with government, academia and industry, while offering a rapid prototyping capability.

Through funding provided by the Office of the Secretary of Defense, Director of Defense, Research and Engineering, the SDR lab team will collaborate with NRL to start building a universal GNU radio hardware/software test bed this year. Once the test bed is completed, it will be made remotely accessible to DoD organizations and external partners by means of the Defense Research Engineering Network. In that way, all partners will be able to test their own software on the universal GNU platform from any location by means of Internet access.

CERDEC, with locations in Fort Monmouth, NJ, Aberdeen Proving Ground, MD, and Fort Belvoir, VA, serves as the US Army's research, development, and engineering center for information technologies and integrated systems. It is one of 10 organizations that comprise the US Army's Research, Development and Engineering Command (RDECOM) organization and is the leading supplier of advanced Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) capabilities, technologies, and integrated solutions. CERDEC's areas of expertise include tactical mobile communications, command and control, RF spectrum dominance, mobile power, sensors, electronic warfare (EW), and surveillance.